Systems and methods for using polyaxial plates

ABSTRACT

Embodiments of the present invention provide a bone fixation assembly that can provide polyaxial fixation. The polyaxial fixation may be provided by fins that protrude from an opening in a bone plate or fins that protrude from a fastener head.

This application is a divisional of U.S. patent application Ser. No.11/996,795, filed Aug. 1, 2008, now allowed, which is the U.S. nationalphase of International Application No. PCT/US2006/028778, filed Jul. 25,2006, and published in English on Feb. 1, 2007, as InternationalPublication No. WO 2007/014192 A2, which application claims the benefitof U.S. Provisional Application Ser. No. 60/702,231 filed Jul. 25, 2005titled “Locking Screw,” the entire contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to orthopedic fixation devicesand bone plating systems for fracture fixation, and particularly tosystems and methods for using bone plates that provide polyaxialfixation of fasteners.

Bone fractures are often repaired by securing a bone plate across thefracture. Depending upon which bone is to be treated, the bone plate maybe straight or curved to match the contour of the bone for which it isdesigned. Bone plates may also be provided in many shapes and sizes. Incases where a bone is severely comminuted or if bone segments aremissing, the use of bone plate and screw systems promotes healing of thefracture by providing a rigid fixation or support structure between thebone and the plate.

Bone plates may be secured to the bone in a number of ways. An existingsolution is a plate and screw system where the screws are locked in theplate. A bone screw is threaded through an opening in the plate and intothe bone. The screw is then secured to the bone plate via threads in thescrew head that cooperate with threaded openings in the bone plate. Thissecures the plate with respect to the bone and provides rigid fixationbecause the relationship between the plate and screw(s) is fixed.Because the head of the locking screw interdigitates with threads in theplate, the plate and screws(s) form one stable system, and the stabilityof the fracture can be dependent upon the stiffness of the construct.Locking a screw into the plate can achieve angular and axial stabilityand eliminate the possibility for the screw to toggle, slide, or bedislodged, reducing the risk of postoperative loss of reduction.However, although may reduce the incidence of loosening, they provideonly one fixed angle relationship between the plate and the screw(s).They have a limited insertion angle because the threads of the head matewith the threads of the hole in one way only. The longitudinal axis ofthe screw lines up with the central axis of the hole, and no angularvariation is allowed. In short, locking screws are unidirectional,limiting their use in some instances.

For example, when treating a severe fracture, fragments may be shatteredand in irregular positions. Although a surgeon may wish to obtain thebenefits of a locking screw and bone plate used together, the angle atwhich the locking screw extends from the plate at a certain opening maynot be the angle that would allow the surgeon to “grab” (or seize, orotherwise secure) the desired, random bone fragment. In this case, thesurgeon may need to secure the plate to the bone somewhere else, or usea non-locking screw. Although non-locking screws do not lock into theplate, they can be inserted at various angles.

Specifically, non-locking screws are secured into bone in the same waythat locking screws are, but they are not secured to the plate. Theirheads are typically rounded where they contact the bone plate. Thus, oneadvantage of non-locking screws is that they can be inserted at variousangles because they are not limited by the thread-to-thread contact oflocking screws with the bone plate. However, if the surgeon desires therigid stable construct of a locking screw and plate, the use of anon-locking screw to obtain the desired angular orientation is notnecessarily optimal.

There have been bone plating systems developed that provide the surgeonwith the option of choosing a non-locking or a locking screw. In someembodiments, these systems provide plates with some threaded holes (thatmay receive with either locking screws or non-locking screws) and somenon-threaded holes (for non-locking screws). There are also systems thatprovide partially threaded slots to allow either non-locking or lockingscrews to be used together. Such combination slots provide surgeons withthe intraoperative choice about whether to use the plate with lockingscrews, non-locking screws, or with a combination of both. Thesecombination slots typically have a partially threaded opening that canreceive either a compression screw or a locking screw. However, becausethese combination slots are only partially threaded, the lockingscrew(s) may not be able to maintain the fixed angular relationshipbetween the screw(s) and plate under physiological loads. Specifically,the locking screws within the plate are only partially captured and thusonly partially surrounded by threads. Under high stress and loadingconditions, the slot may distort and allow the fixed angularrelationship between the locking screw and plate to change. This canresult in loss of fixation or loss of established intraoperative plateorientation. Moreover, the locking screw can still only be inserted at asingle angle—the predetermined angle defined by the manufacturer.

Additionally, current bone plate and screw systems still limit asurgeon's ability to both (a) lock a fastener with respect to the boneplate, but still (b) allow the fastener to extend from the bone plate atvarious angles. Locking screws lock into the plate, but only in a singleangular configuration, and non-locking screws allow various angleconfigurations, but they do not provide a stable construct with theplate. Accordingly, none of these options allow a surgeon to capturebone fragments that do not fall in line with the axis of the openingprovided on the plate in a rigid fashion. As example of this problem isshown in FIG. 21. Thus, currently available options can still lead tomalalignment and poor clinical results.

There have, however, been some attempts to provide polyaxial lockingsystems. For example, one effort includes providing holes that acceptfixed angle locking pegs and multidirectional locking pegs, with athreaded cap inserted over the multidirectional peg to hold it intoplace. Such a system can be cumbersome to use because although themultidirectional peg can be inserted at any angle, the surgeon thenneeds to thread a small cap onto the top of the peg head and into theplate, requiring an extra step, extra time, and extra instrumentation.Such systems also fail to allow the use of non-locking members inconjunction with the locking and multidirectional pegs.

Other systems that have attempted to offer polyaxial fixation includeproviding a bone plate with inserts at the hole peripheries made out ofa deformable material, with the remaining part of the plate made oftitanium. The plate is manufactured and the inserts are then pushed intothe hole peripheries and engaged in place by deformation and pressure.When screws are inserted, the inserts deform and are compressed betweenthe edges of the holes of the plate, which holds the screws and insertsin place. Challenges with such systems are that they cannot be used withnon-locking screws, the inserts do not have the strength to receive andhold a regular locking screws, (i.e., they do not provide the surgeonwith options), and plates with deformable inserts are more expensive tomanufacture than regular bone plates. Other attempts have failed toprovide adequate locking mechanisms. Another attempt at polyaxialfixation includes a plate with holes that have an internal jacket withrecesses that extend away from the axis of the hole or into the internaljacket surface. This attempt is described in International ApplicationWO 2005/018472, titled Bone Plate. The internal jacket surface of theplate described in that application is threaded or has ribs orprotuberances. A bone screw is intended to be pulled into the hole ofthe plate by the internal jacket surface. If the bone screw head isthreaded, when the screw in inclined, the threaded head is intended to“jump over” the pitches of the threads in the hole of the plateinterrupted by the recesses, without “cutting through” them. The goal ofthe invention is provide a bone plate that can have bone screwsintroduced at an angle that is different from the specified axis of thehole and secured into position.

However, some of the problems encountered by this attempted solution arethat (1) threaded openings in bone plates typically require the plate tobe of a certain thickness and thus, do not lend themselves to use with athin plate, (2) threaded openings can be difficult and more expensive tomanufacture than non-threaded openings in a bone plate, and (3) threadedopenings can take more effort in use because the surgeon needs to havethe appropriate alignment for use. Moreover, the threads of thisapplication are short because they are interrupted by the recesses so itis likely that a fastener will not actually “grab” the threads to getgood engagement.

Accordingly, there exists a need for an improved bone plating systemthat overcomes the deficiencies of the prior art. There is a need for asystem that provides a stable connection between a bone and a bone plateusing a fastener that permits different angles to be obtained betweenthe bone plate and the fastener, while the fastener also locks into thebone plate. This would allow surgeons to capture random bone fragmentsthat are in irregular positions, for example, in cases of severefractures with highly fragmented bone fragments. In these and othercases, it would be advantageous to provide a fastener and plate systemthat allows the surgeon to choose the angle at which the screw isinserted through, and rigidly affixed in, an opening of the plate.

Such an improvement would allow a surgeon to direct the fastener towardbone fragments that are not necessarily located directly beneath theopening in the plate. It would also provide flexibility in the placementof the plate in relation to the bone fracture. Allowing surgeons tochoose the angle at which the fastener is inserted into the plate wouldlead to better tailoring of the system to the specific nature of thebone fracture to be treated. It would also allow surgeons to adjusttheir strategy as necessary after the surgical site has been accessed,but prior to insertion of the fastener into bone material. Additionally,in situations where it is desirable to insert a fastener into a plate ina coaxial or polyaxial direction, the embodiments described herein wouldprovide such a secure fit.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention relate to a bone fixation assemblythat can provide polyaxial fixation. The polyaxial fixation may beprovided by fins that protrude from an opening in a bone plate or finsthat protrude from a fastener head. For example, according to one aspectof the invention, there may be provided a polyaxial bone fixationassembly comprising

-   -   (a) a bone plate comprising a lower surface, an upper surface        and at least one opening extending from the lower surface to the        upper surface;    -   (b) a fastener that is insertable through the opening; and    -   (c) at least one member of co-operation between the opening and        the fastener comprising a plurality of protruding fins located        within the opening or on the fastener.

In a specific aspect or embodiment, the opening has a non-threaded innersurface and wherein the fins are located on the inner surface.

Further embodiments have fins that are a series of concavely indented,inwardly protruding fins that are adapted to secure a threaded head of afastener in place at varying angles.

According to a further embodiment, the opening is further defined by around circumference at the upper surface and a jagged circumferenceformed by the protruding fins at the lower surface.

According to a further embodiment, the protruding fins form a concaveportion of the inner surface.

According to an even further embodiment, the protruding fins have basesthat meet the inner surface in substantially the same plane.

According to another embodiment, the fastener has a threaded headadapted to engage with the protruding fins.

Another embodiment provides fins that have a tapered shape, a straightshape, a rectangular shape, or a triangular shape.

A further embodiment provide a bone plate with the opening located onthe head.

In further specific aspect or embodiment, the fastener has a head withfins, wherein the fins are adapted to cooperate with threads in a boneplate.

According to another embodiment, the fins are provided in more than onelayer.

Another embodiment provides the opening in the bone plate with one ormore rectangular threads.

In a further embodiment, the fins are trapezoidally-shaped, rounded,oval, rectangular, curved, rhomboid, diamond-shaped, or triangular. Thefins may also have the edges of fins taper inwardly, outwardly, or areabout parallel with one another.

According to a further embodiment, the bone plate is adapted to contacta femur, a distal tibia, a proximal tibia, a proximal humerus, a distalhumerus, a clavicle, a fibula, an ulna, a radius, bones of the foot, orbones of the hand.

Further embodiments have a bone plate with one or more of the followingfeatures:

-   -   (a) contoured, straight, or flat;    -   (b) a head portion that is contoured to match a particular bone        surface;    -   (c) a head that flares out to form an L-shape, T-shape, or        Y-shape; and (d) any combination thereof.

Other embodiments provide the bone plate with one or more of the followopenings:

-   -   (a) a threaded opening;    -   (b) a non-threaded opening; (c) an opening adapted to receive        locking or non-locking fasteners;    -   (d) a combination slot; or;    -   (e) any combination thereof.

Other aspects of the invention also provide methods for securing a boneplate to a bone using polyaxial fixation. For example, one aspectprovides a method for securing a bone plate to a bone using polyaxialfixation, comprising:

-   -   (a) providing a bone plate comprising a lower surface, an upper        surface, and at least one opening extending from the lower        surface to the upper surface, the opening having a non-threaded        inner surface with one or more protruding fins located on the        inner surface;    -   (b) providing a fastener having a shaft and a head, the head        having at least one set of threads adapted to cooperate with the        protruding fins;    -   (c) inserting the fastener into the opening of the bone plate        and allowing the at least one set of threads to engage the fins        of the plate; and    -   (d) securing the bone plate to bone.

Another aspect provides a method for securing a bone plate to a boneusing polyaxial fixation, comprising:

-   -   (a) providing a bone plate comprising a lower surface, an upper        surface, and at least one opening extending from the lower        surface to the upper surface; the opening having one or more        threads;    -   (b) providing a fastener having a shaft and a head, the head        having at least one set of fins adapted to cooperate with        threads of the plate;    -   (c) inserting the fastener into the opening of the bone plate        and allowing the one or threads to engage the fins of the        fastener head; and    -   (d) securing the bone plate to bone.

Embodiments of the above aspects include using polyaxial fixation todraw a bone fragment into alignment.

Another embodiment includes inserting a locking screw or a non-lockingscrew into the bone plate.

“Embodiment” as used herein can be considered to mean an aspect orobject of the invention, and vice versa.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a perspective view of a bone plate having fins according toone embodiment of the invention with a fastener inserted therein.

FIG. 2 shows a top perspective view of an opening in a bone plateaccording to one embodiment of the invention.

FIG. 3 shows a top view of a bone plate having multiple openings, with afastener inserted therein.

FIG. 4 shows an underneath view of the bone plate of FIG. 3.

FIG. 5 shows a side perspective view of a bone plate with fastenersinserted therein to illustrate a few of the multiple angles at which theplate can receive a fastener.

FIG. 6 shows an example of a fastener for use with various bone platesdescribed herein.

FIG. 7 shows a top plan view of an alternate embodiment of an opening ina bone plate.

FIG. 8 shows a perspective view of the bone plate of FIG. 7.

FIG. 9 shows a top plan view of a further embodiment of an opening in abone plate.

FIG. 10 shows a perspective view of the bone plate of FIG. 9.

FIGS. 11-15 show alternate shapes and types of bone plates that may beused with various embodiments of this invention.

FIG. 16 shows a cross-section view of an alternate embodiment having afinned fastener in place in a bone plate.

FIG. 17 shows a side perspective view of a fastener having a finned headaccording to one embodiment of the invention.

FIG. 18 shows a top perspective view of the fastener of FIG. 17.

FIG. 19 shows a top perspective view of a bone plate that may be used toreceive the fastener of FIGS. 17 and 18.

FIG. 20 shows a cross-section of the threads of the plate of FIG. 19.

FIG. 21 shows an example of a fracture that may be treated with variousembodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention provide a bone fixation assemblythat can accept and fix fasteners at a plurality of angles. A specificembodiment of a bone fixation assembly 10 is shown as a bone plate 12and fastener 80 in FIG. 1. As shown in more detail in FIGS. 2-4, boneplate 12 has a lower surface 14 and an upper surface 16 and one or moreopenings 18 that extend from the lower surface 14 to the upper surface16.

The embodiments described herein may be used in connection with any typeof bone plate, non-limiting examples of which are shown in FIGS. 11-15.Plate 12 may be adapted to contact one or more of a femur, a distaltibia, a proximal tibia, a proximal humerus, a distal humerus, aclavicle, a fibula, an ulna, a radius, bones of the foot, or bones ofthe hand. The bone plate may be curved, contoured, straight, or flat. Itmay be a periarticular plate or a straight plate. An example of astraight plate in shown in FIG. 11. Plate may have a head portion thatis contoured to match a particular bone surface, such as a metaphysis ordiaphysis, flares out from the shaft portion, that forms an L-shape,T-shape, Y-shape, with the shaft portion, or that forms any otherappropriate shape to fit the bone to be treated. An example of aT-shaped plate is shown in FIGS. 12-15, the openings on the plates inthose figures are described in more detail below.

Bone plate 12 may be comprised of titanium, stainless steel, cobaltchrome, plastic—such as polyetheretherketone (PEEK), polyethylene, ultrahigh molecular weight polyethylene (UHMWPE), or a carboncomposite—resorbable polylactic acid (PLA), polyglycolic acid (PGA),combinations or alloys of such materials or any other appropriatematerial that has sufficient strength to be secured to and hold bone,while also having sufficient biocompatibility to be implanted into abody. Although the above list of materials includes many typicalmaterials out of which bone plates are made, it should be understoodthat bone plates comprised of any appropriate material are within thescope of this invention.

Opening 18 of plate 12 is shown having a central axis 20, and it isadapted to receive a fastener. The fastener may be any typical, standardlocking fastener or a non-locking fastener, although the embodimentsdescribed herein are intended for particular use with locking fastenersthat have a series of threads on their heads. FIGS. 5-6 show examples offastener 80 that may be used in accordance with embodiments of thisinvention. As shown specifically in FIG. 6, fastener 80 has a shaft 82and a head 84. Shaft 82 may be threaded or otherwise configured toengage bone. It may be fully threaded, partially threaded, comprise ahelical blade, and/or may comprise one or more tacks, deployable talons,expanding elements, or so forth. Any feature that allows shaft 82 toengage bone is considered within the scope of this invention and may bereferred to generally as a “threaded shaft” for the sake of convenience.It is also possible, however, that shaft 82 is not threaded, so thatfastener 80 takes the form of a peg or a pin. This alternativeembodiment may be preferred in certain procedures where, for instance,the main goal is to prevent tilting of a bone segment, or in procedureswhere there is no concern of fastener 80 pulling out from the bone andhence no need for shaft 82 to be threaded or otherwise configured toengage bone. For the sake of reference, shaft 82 is also shown having alongitudinal axis 86. The end of shaft 82 may be a self-tapping orself-drilling tip, as shown in more detail in FIG. 5.

The head 84 of fastener 80 preferably has at least one set of threads88. Threads 88 are typically any standard-type thread. For example, thethreads 88 may be a continuous ridge or a non-continuous ridge. It maycomprise a portion of a revolution, one complete revolution, multiplerevolutions, a single lead, or multiple leads, or any other threadsknown in the art. Additionally or alternatively, head 84 of fastener 80may include any other surface that will engage with and seat withinspecific features of plate (described further below). For example, head84 may have a series of dimples, ridges, bumps, textured areas, or anyother surface that can secure fastener 80 as described herein. As willbe described in more detail below, threads 88 of head are adapted toengage, associate with, or otherwise cooperate with fins 24 of opening18. In short, any type of threaded fastener head is intended for usewith various embodiments of this invention.

Referring to FIG. 2, it can be seen that the embodiment shown has anopening 18 with an inner surface 22 that is defined by a series ofconcavely indented, inwardly protruding fins 24. Fins 24 extend intoopening 18 toward central axis 20. The bases 26 of fins 24 form aconcave portion 28 at or near a round circumference 30 of upper surface16. (The term “round” circumference is intended to refer to any roundshape, such as a circle, an oval, an egg-shaped circumference, or anyother opening shaped to receive the head of a fastener 80.) The bases 26of the fins 24 may all meet in substantially the same plane and thenangle downwardly and inwardly at a similar angle or slope.

It bears noting that the concave portion 28 is smooth and non-threaded.In fact, there are not any threads on concave portion 28 or anywhere oninner surface 22 of opening 18. The lack of threads helps ease themanufacturing of plate 12, and allows plate be manufactured as thinly asdesired.

For example, the thickness of plate 12 and the dimensions of fins 24 aretypically dependent upon the pitch and threads of fastener 80. Forexample, a larger plate 12 for use with a larger fastener (e.g., for useon a femur bone) will likely be thicker and will have larger and thickerfins than a smaller plate (e.g., for use on a smaller bone). In specificembodiments, the fins 24 are particularly thin so that they can be movedup or down and deformed upon pressure. In some embodiments, the fins maybe pressed toward the edges of the plate opening. A non-limitingexemplary range of thicknesses for fins may be from about 0.5 mm toabout 5 mm, although larger and smaller sizes are possible. In theory,the fins 24 are intended to fit between crimps on the threadform offastener 80, as shown in FIG. 1.

Providing a non-threaded inner surface 22 also allows the fastener 80 tobe inserted into opening 18 at any desired angle, because there are notany threads to interfere with the desired angle, as illustrated by FIG.5. The fins 24 are intended to slightly bend or deform in order tosecure the fastener 80 in place in opening 18. Fins 24 actually engagethreads 88 or other surface of fastener 10.

Referring back to FIG. 2, in the embodiment shown, as fins 24 extendtoward central axis 20, they taper to form tapered sides 32. The finsend at rounded tip 34, although tips 34 can be pointed, square,rectangular, or any other appropriate configuration. For example, asshown in FIGS. 7 and 8, fins 24 may have straight edges or sides 42 andstraight ends 44. This embodiment shows fins 24 that are partiallyrectangular-shaped. The openings 46 between fins 24 are slit-shaped.

An alternate embodiment is shown in FIGS. 9 and 10, which illustratefins 24 with a more triangular shape. In this embodiment, fins 24 areshown having sides 52 that taper inwardly and edges 54 that are flat andsmall, forming the apex area 56 where sides 52 come to an end. Openings58 between fins 24 are more elongated than openings 46. Both sets ofopenings 46, 58 in these alternate embodiments are shown having roundedbacks 60, where they meet inner surface 22 of opening 18. It should beunderstood however, that these are merely examples of fin 24 shapes andopenings 46, 58 and that any appropriate shapes are possible andconsidered within the scope of this invention. Non-limiting examplesinclude trapezoidal, square, round, circular, triangular (with a pointedtip instead of apex area 56), and any other possible option.

As shown in FIG. 4, a second circumference 36 at the lower or underneathsurface 14 of plate 12 may appear to be more jagged than the roundcircumference 30 at the upper surface 16 due to the fins 24 forming aportion of lower surface 14. The circumference can appear almost“flower-like”—each fin 24 appears to form a petal of the circumference.Alternatively, for the embodiments of FIGS. 7-10, the secondcircumference will appear similar to the shape created by fins 24.

Although the figures show an opening 18 with about five to eight fins24, it should be understood that any number of fins 24 is consideredwithin the scope of this invention. For example, there may be two orthree fins, or ten or twenty or more fins 24, depending upon the platefor which the opening 18 is intended for use.

The primary purpose of fins 24 is to grasp one or more threads 88 of athreaded head fastener in order to secure the fastener in place in thebone plate 12, but at any angle. For example, as opposed to threadedopenings (which engage the threads of the head of the fastener in oneway only, limiting the surgeon's ability to angle the fastener asdesired), the fins 24 of this embodiment are still intended to securethe threads of the head of fastener in place, but at any angle. As thefastener is inserted, its threads start to engage the fins 24, as shownin FIG. 1. As discussed above, the fins 24 may be very thin so that asthe head threads 88 start to grab fins 24, the fins 24 may move up ordown as appropriate to engage the threads 88 and secure the fastener 80.In short, the threads 88 engage fins 24 (or fit in between fins 24). Inmost cases, this movement of fins 24 is a permanent deformation, so thatthe fins cannot flex back and allow the fastener to work its way out.

As discussed above, finned openings 18 may be provided on all types ofbone plates, examples of which are shown in FIGS. 11-15. FIG. 11 shows aspecific example of an opening 18 with fins 24 (referred to as a finnedopening 18), a smooth opening 60, a threaded opening 62, and aprovisional pin opening 64. Other options are holes that can be usedwith either a threaded or non-threaded fastener, as well as combinationslots. It should be understood that these various types of openings maybe used on any types of bone plates, in any combination and in any size,examples of which are shown in FIGS. 12-15. FIG. 12 shows a plurality offinned openings 18 in the head 70 of bone plate 12. This may helpachieve better fixation of a fractured bone, because the fastener can beinserted at various angles to capture “renegade” or random bonefragments that have split from the bone during fracture, but stillsecure the bone fragments to the plate. For example, if a wrist bone isbroken, there will be numerous fragments that may shatter in variousdirections. The plates 12 with finned openings 18 described herein canbe used to place a fastener 8—at various angles in order to capture therenegade fragments that would otherwise not be secured to a bone plateusing only a locking or a non-locking fastener. It should additionallybe understood that other types of openings (in addition to or instead offinned openings 18) may be present in the head 70, as well as elsewhereon plate 12.

As previously mentioned, fastener 80 may be any typical fastener, madeout of any appropriate material. It will typically have a bore forreceiving a driver in order to secure fastener into bone and into plate12. The receiving bore may be any size and shape, for example, it mayhave a hexagonal configuration to receive a corresponding hexagonaldriver, a Phillips screw head, a flat-head, a star configuration, Torx,or any other appropriate configuration that can cooperate with a driverto place fastener.

Turning now to the methods of implantation, the surgeon accesses thesurgical site of interest, which can be an internal site at which a bonefracture is located that requires stabilization to ensure properhealing. The fracture may be reduced with conventional forceps andguides (which are known to those in the art), and a bone plate ofappropriate size and shape is placed over the fracture site. In someinstances, the bone plate may be temporarily secured to the bone usingprovisional fixation pins. In the bone plates shown in FIGS. 11 and 12,provisional fixation pins may be used through either the provisional pinopenings, or any other opening (threaded or non-threaded or finned) inthe plate. Provisional fixation provides for temporarily securing thebone plate to the bone before placing fixation screws through the boneplate, so that one can be certain the bone plate is properly positionedbefore placing bone screws for permanent fixation of the bone plate tothe bone. Moreover, with provisional fixation, x-rays can be taken ofthe bone plate/construct without excess instruments in the field ofview.

Once the plate 12 is secured at a desired location in relation to thefracture (typically using one or more provisional fixation pins,although any other appropriate method may be used), the surgeon thenidentifies an insertion angle, or the direction along which fastener 80is to be inserted through a selected opening 18 and driven into bonematerial. If bone plate 12 includes more than one opening, as shown inthe figures, the surgeon also selects the specific opening to be used.After selecting the desired insertion angle and opening, the surgeoninserts shaft fastener 80 through opening 18 until the tip contacts bonematerial. In some cases, a hole may need to be drilled or tapped intothe bone along the insertion angle to facilitate the initial tapping orinsertion of fastener 80. The surgeon then uses an appropriate drivingtool in the receiving bore of head 84 to manipulate the fastener 80 intoplace.

Because fastener 10 may be inserted at angles other than the alignedwith the central axis 20 of the opening 18, as shown in FIG. 5, fastener80 may be used to grab or secure bone fragments that are out of linewith the traditional angle at which a locking screw would normally beinserted. The surgeon may need to toggle or maneuver the fastener 80 inorder to secure and draw in displaced bone fragments.

Once the bone fragment is secured, the fastener 80 is ready to besecured to the plate 12. As fastener 80 is driven further into bone, itis also drawn further into plate 12. As threads 88 of fastener head 84begin to contact fins 24, the fins are allowed to engage within thethreads to hold the fastener 80 in place in the desired angle, evenangles that are other than in line with the central axis 20. The actionof engagement between fins 24 and threads 88 rigidly affixes fastener 80to the bone plate 12 at the desired insertion angle. In someembodiments, the surgeon may then use traditional locking and/ornon-locking screws in other openings on plate. This can help furthersecure the bone plate to the bone fracture if needed. One advantage ofopening 18 is that it is adapted to receive any one of the potentialfasteners that may be used with plate 12.

In some instances, once all fasteners and/or screws are placed, thesurgeon may place covers over the unused openings, particularly if thereare any unused openings that cross the fracture in order to strengthenthe plate 12. Additionally or alternatively, the surgeon may use bonegraft material, bone cement, bone void filler, and any other material tohelp heal the bone.

An alternate embodiment of a fixation assembly is shown in FIGS. 16-18.These figures show a fastener 102 with a finned head 104. Specifically,the finned head 104 comprises a receiving bore 106 at its upper portion108 and at least one set of extending fins 110 around the main portion112 of the head 104. Fins 110 are shown as being square ortrapezoidally-shaped with tapered edges, although they may be any othershape, such as rounded, oval, rectangular, curved, rhomboid,diamond-shaped, triangular or any other appropriate shape. The edges 111of fins 110 may taper inwardly, outwardly, or be about parallel with oneanother. Fins 110 may be provided in a single row around head 104 orlayered in multiple rows as shown. If layered in multiple rows, eachindividual fin 110 may be directly above another fin (so the top of thefastener 100 looks like that shown in FIG. 18). Alternatively, eachindividual fin 110 in a lower layer may be offset from a fin in a higherlayer. The number of fins 24 in a set may also vary from about two orthree up to any desired number that can fit on main portion 112 of head104. As with the fins 24 of opening 18 described above, the fins 110 arepreferably quite thin, the thickness varying depending upon the use offastener and plate. For example, a larger fastener 102 for use with alarger plate (e.g., for use on a femur bone) will likely have larger andthicker fins 110 than a smaller fastener (e.g., for use on a smallerbone). In specific embodiments, the fins 110 are particularly thin sothat they can be moved up or down or compressed upon pressure. Anon-limiting exemplary range of thicknesses for fins may be from about0.5 mm to about 5 mm, although larger and smaller sizes are possible. Intheory, the fins 110 are intended to fit between the threadform ofplate. Fastener may also have a shaft 114 that is threaded orunthreaded, as described above with respect to fastener 80.

Fastener 102 may be used with any bone plate that has a threadedopening. Any of the examples shown in the figures are described abovemay be used with fastener 102. One option of a specific bone plate thatcan be used with fastener 110 is shown in FIG. 19. This bone plate 120has Acme threads 124 that have a more rectangular shape than thepointed, sharp threads that are typically used in bone plates. As shownin FIG. 20, opening 122 has threads 124 that end at their edges 126 in arectangular shape. Providing a rectangular shape with a flatter edge 126allows a larger channel for the fins 110 to engage. In an even morespecific embodiment, the threads 124 may be angled at about 15-20° offof the central axis 130 of opening 122, and even more specifically, atabout 18° off of the central axis 130.

An example of the method of use is similar to that describe above. Asfastener 102 is being inserted into bone plate 120 (although it shouldbe understood that any traditional bone plate may be used; Acme threadsare not a requirement), the fins 110 are intended to engage threads ofthe plate and, much like the fins of the bone plate described above,fins 110 are very thin so that as the threads of plate start to grab thefins 110, the fins 110 may move up or down as appropriate to engage thethreads of plate and secure the fastener 102 in place, as shown in FIG.16. In most cases, this movement of fins 110 is a permanent deformation,so that the fins cannot flex back and allow the fastener to work its wayout.

The foregoing description of exemplary embodiments of the invention hasbeen presented only for the purposes of illustration and description andis not intended to be exhaustive or to limit the invention to theprecise forms disclosed. Many modifications and variations to thestructures and methods recited above and shown in the drawings arepossible without departing from the scope or spirit of the abovedisclosure and the following claims. The embodiments were chosen anddescribed in order to explain the principles of the invention and theirpractical application so as to enable others skilled in the art to makeand utilize the invention and various embodiments and with variousmodifications as are suited to the particular use contemplated.Alternative embodiments will become apparent to those skilled in the artto which the present invention pertains without departing from itsspirit and scope.

What is claimed:
 1. A method for securing a bone plate to a bone usingpolyaxial fixation, comprising: (a) inserting at least one fastener intoan opening of a bone plate, the at least one fastener being at leastpartially threaded and having a head portion and a shaft portion and thebone plate comprising a lower surface, an upper surface and the openingextending from the lower surface to the upper surface, the openingadapted to receive the at least one fastener without being tapped by theat least one fastener, the opening having an inner surface with aplurality of non-circumferential fins integrally connected to eachother, integrally connected to and protruding from, the inner surface,and allowing the fins to engage the threads of the at least onefastener; (b) orienting the at least one fastener at any one of aplurality of angles relative to the opening such that at least a portionof each of the engaged fins is independently moved toward the uppersurface or toward the lower surface; and (c) securing the bone plate tobone with the at least one fastener.
 2. The method of securing a boneplate to a bone using polyaxial fixation of claim 1, wherein either alocking screw or a non-locking screw is inserted in the opening.
 3. Themethod of securing a bone plate to a bone using polyaxial fixation ofclaim 1, wherein the at least one fastener is removed and re-insertedinto an opening of the bone plate at any one of a plurality of angles.4. The method of securing a bone plate to a bone using polyaxialfixation of claim 1, wherein inserting the at least one fastener intothe opening in the bone plate step (a) further comprises using polyaxialfixation to draw a bone fragment into alignment.
 5. The method ofsecuring a bone plate to a bone using polyaxial fixation of claim 1,wherein one or more of the fins has tapered sides and ends at a roundedtip.
 6. A method for securing a bone plate to a bone using polyaxialfixation, comprising: (a) inserting a fastener into an opening of a boneplate with the fastener oriented at any one of a plurality of anglesrelative to the opening without tapping the bone plate, with threads ofthe fastener engaging a plurality of non-circumferential fins integrallyconnected to each other, integrally connected to and protruding from, aninner surface of the bone plate defining the opening, wherein the boneplate comprises a lower surface and an upper surface, and the openingextends from the lower surface to the upper surface, the fins each beingindependently movable toward the upper surface or toward the lowersurface in response to engagement with the threads of the fastener; and(b) securing the bone plate to bone with the fastener.
 7. The method ofsecuring a bone plate to a bone using polyaxial fixation of claim 6,wherein the opening has a central axis, and wherein (a) inserting thefastener comprises: inserting the fastener at an angular offset from thecentral axis such that the engagement of the fins with the fastenerretains the fastener in the opening at the angular offset.
 8. The methodof securing a bone plate to a bone using polyaxial fixation of claim 6,wherein the method comprises permanently deforming the engaged finsthrough engagement with the fastener.
 9. The method of securing a boneplate to a bone using polyaxial fixation of claim 6, wherein the finsare provided as a series of concavely indented, inwardly protruding finsthat are adapted to secure a threaded head of the fastener in place atany one of the plurality of angles.
 10. The method of securing a boneplate to a bone using polyaxial fixation of claim 6, wherein theprotruding fins form a concave portion of the inner surface.
 11. Themethod of securing a bone plate to a bone using polyaxial fixation ofclaim 6, wherein the protruding fins have bases that meet the innersurface in substantially the same plane.
 12. The method of securing abone plate to a bone using polyaxial fixation of claim 6, wherein thefins have a tapered shape or a straight shape.